When it comes to exchanging secure information over an insecure channel, this approach is considered. It all depends on the nature of photons in which the third polarization is focused. It can easily be trusted when it comes to exchanging the Secret keys without facing any issue.

What is Quantum Cryptography?

What are the differences between modern cryptography and quantum cryptography?

$\begingroup$Can you identify what you are substantively asking about that is not already addressed in the other questions?$\endgroup$
– Squeamish OssifrageJun 17 '19 at 19:27

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$\begingroup$@SqueamishOssifrage It seems different to me because this is asking about terminology. The former isn't an answer because, if OP doesn't know what quantum cryptography is, an answer explaining why it's secure isn't helpful. The latter also requires you to know what quantum cryptography is to ask about QKD. While they are extremely related, I think this question is just different enough to be on-topic.$\endgroup$
– forestJun 18 '19 at 3:38

$\begingroup$@forest What makes a question a duplicate is not whether the text of the question is the same, but whether the answers are already subsumed by the answers to existing questions—that is, whether there is anything in this question that is not addressed by the other questions. So, after you read the answers to the other questions, what is left that you are still wondering about in this question?$\endgroup$
– Squeamish OssifrageJun 18 '19 at 20:35

1 Answer
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Today's "normal" cryptography relies mostly on mathematical principles. For example RSA is based on the practical difficulty of the factorization of the product of two large prime numbers, the so-called "factoring problem".

But if quantum computers were available they would break some of today's cryptography used on classical computers, i.e. RSA or Diffie-Hellman. We would then have to switch to post-quantum cryptographic algorithms like Supersingular isogeny key exchange. So ultimately, I think, we would just switch to quantum-resistant algrorithms and go on with our lives.